1. Field of the Invention
The present invention relates to a lithographic apparatus and methods.
2. Related Art
A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In such a case, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g., including part of, one, or several dies) on a substrate (e.g., a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Conventional lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at once, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.
The lithographic apparatus may be provided with an actuator configured to exert a force on certain parts within the lithographic apparatus. For example, a positioning system may be provided with an actuator to position a support constructed and arranged to hold a patterning device and/or may be used to position a substrate table constructed to hold a substrate. The positioning system may be provided with an elongated structure, for example, a so-called beam configured to transfer the forces of the actuator to the support and/or the object table. The elongated structure may be sensitive to vibrations leading to inaccuracies in the positioning system and/or risks that certain parts of the drive may fail.